1. Technical Field
The present invention relates to a mask, a mask chip, a manufacturing method of the mask, a manufacturing method of the mask chip, and an electronic device.
2. Related Art
An organic EL (electroluminescent) panel is composed of highly-responsive light emitting display elements in a layered structure of thin films. Thus, the organic EL panel has a light weight and can be used for a display apparatus providing a superior moving image. Thus, the organic EL panel recently has attracted much attention as a display panel for a flat panel display (FPD) television for example. A representative manufacturing method of the organic EL panel is disclosed in Appl, Phys, Lett, Vol. 51, No.12, p.p. 913-914, (1987). Specifically, the organic EL panel is manufactured in a manner as described below. A photolithographic technique is used to pattern a transparent anode (e.g., ITO (indium tin oxide)) to have a desired shape. Then, an organic material for example is formed and layered on the pattern by a vacuum evaporation apparatus. Next, a metal anode film having a low work function (e.g., MgAg) functioning as a cathode is vapor-deposited on the organic material. Finally, a light-emitting element thus formed is closed and sealed in inert gas atmosphere so that the light-emitting element has a contact with moisture or oxygen.
The organic EL panel also can provide various luminescent colors by changing its light-emitting material. For example, a method has been suggested that uses a thin high definition metal mask to form light-emitting elements of red, green, and blue for each pixel. This method intends to provide a full-color organic EL panel providing a sharp image by a close contact between a metal mask and a glass substrate by a magnet to vapor-deposit the glass substrate and the magnet via the mask (see JP-A-2001-273976 for example).
However, the above metal mask described in JP-A-2001-273976 has a disadvantage as described below. Specifically, when an organic EL panel has an increased size in order to provide a larger screen, a metal mask for the panel also must have an increased size. However, it is very difficult to accurately manufacture such a metal mask that has a large size (large area) and that has a thin thickness. Furthermore, the metal mask has a thermal expansion coefficient that is much higher than that of a glass substrate for an organic EL panel. Due to this reason, the metal mask expands with a rate much higher than that of the glass substrate due to the heat radiation during vapor deposition. This causes, when this metal mask is used to produce a large-size organic EL panel, an increase in a cumulative error value due to the thermal expansion. Thus, the use of the metal mask has been limited to the manufacture of a small to medium size panel having a size of 20 inches at most.
Thus, another method has been suggested that manufactures a vapor deposition mask by using a silicon substrate instead of the metal mask. This method intends to use a silicon substrate itself as a mask using a semiconductor manufacture technique (e.g., photolithographic technique, dry etching technique). Silicon has substantially the same thermal expansion coefficient as that of glass. This prevents the thermal expansion-induced dislocation between a silicon mask and a glass plate as a substrate on which film formation is performed. Silicon also can provide a high machining accuracy (see JP-A-2001-185350 for example). Recently, silicon wafers having a diameter of 300 millimeter have been manufactured. The use of this silicon wafer can produce a vapor deposition panel corresponding to a display panel having a diagonal of about 10.5 inches.
JP-A-2001-273976 is an example of related art.
JP-A-2001-185350 is an example of related art.
By the way, recent televisions generally used for a domestic use mainly have large-size screens ranging from 30 to 40 inches. However, when a silicon-based vapor deposition mask is used to form a light-emitting layer or the like of an organic EL device, the diameter of 300 millimeters of the silicon wafer as described above has caused a limitation on the manufacture of a vapor deposition mask adapted to a large-size screen.